1. Field of the Invention
The present invention relates to a radar system, and more particularly to a radar system which is mounted on a vehicle and which can detect degradation of the sensitivity of a radar apparatus.
2. Description of the Related Art
A radar system mounted on a vehicle has conventionally come into a practical use for the purpose of detection of any obstacle to prevent the vehicle from colliding with the obstacle around the vehicle in running in a narrow alley or putting the vehicle in a garage. Also, in recent years, a radar system has been developed to catch a detection object in a relatively long distance from the vehicle at a high speed in a high precision as a warning apparatus to prevent the vehicle from colliding with a preceding vehicle or as an Adaptive Cruise Control (ACC) to control the vehicle to run while keeping a distance to the preceding vehicle constant.
Here, a radar apparatus of the above radar system mounted on the vehicle is generally installed in a bumper section of the vehicle or a front grill in a front portion of the vehicle. Therefore, it is easy for snow to accrete on a radome of the radar apparatus in case of snowfall. Also, when snow containing much water accretes, the transmission loss of radar wave becomes large. Therefore, the detection sensitivity of the radar system reduces uniformly over all the azimuth directions, so that the distance measuring range of a detection object becomes short.
For this reason, in Japanese Laid Open Utility Model Application (JP-U-Showa 60-173084: a first conventional example), a temperature sensor and a water sensor are provided for the radome of the radar apparatus. An electric current is supplied to a resistor, which is provided for the radome, based on the detection results of the sensors to melt snow and ice. In this way, the sensitivity degradation of the radar system due to snow or ice is prevented.
Also, in Japanese Laid Open Patent Application (JP-A-Heisei 6-59024: a second conventional example), a plurality of electrodes are provided on the whole surface of a radome of a radar apparatus. A voltage or current between these electrodes is detected. In this way, ice formation or adhesion of muddy water on the radome surface is detected.
However, in the radar systems of the first and second conventional examples, the structure of the radome or the radar system becomes complicated to increase the cost of the radar system.
Also, the degree of the sensitivity degradation of the radar system depends on a quality of snow accretion on the radome. Also, even if the accreted snow is melt into water with the heat by a heater provided for the radome or the radiation heat from an engine once,the water sometimes froze again during the running of the vehicle. In this way, the accretion situation of snow and ice changes dependent on the running state of the vehicle. It is difficult to prevent the sensitivity degradation of the radar system due to snowfall by only the measure based on the surface temperature of the radome and the local wetting situation.
In conjunction with the above description, an FM radar apparatus is described in Japanese Laid Open Patent Application (JP-A-Heisei 10-282229). In this reference, a transmission FM signal and a reception FM signal are mixed to obtain a beat signal (10a). A low frequency component of the beat signal (10a) is filtered by a low pass filter (12), A/D converted by a converter (13), and then is subjected to a fast Fourier transformation (FFT) by an FFT converter (14) to produce a detection signal. A control unit (15) compares the detection signal and a corresponding stored signal to detect contamination of a radome (8). The control unit (15) increases a frequency change quantity of a FM signal per a unit time on the detection of the contamination. Thus, the contamination of the radome is detected without providing any sensor to the radome.
Therefore, an object of the present invention is to provide a radar system which can estimate existence or non-existence of accretion of snow or ice.
Another object of the present invention is to provide a radar system which can estimate a melting state of an accreted snow or ice.
Still another object of the present invention is to provide a radar system which can estimate the sensitivity degradation of a radar apparatus.
Yet still another aspect of the present invention is to provide a radar system in which the accreted snow or ice can be removed when the sensitivity degradation of a radar apparatus is estimated.
It is an object of the present invention to provide a radar system in which the sensitivity degradation of the radar system can be prevented with a simple structure.
Another object of the present invention is to provide a method of keeping the sensitivity of a radar apparatus in the above radar systems.
In order to achieve an aspect of the present invention, a radar system mounted on a vehicle includes a radar apparatus, a radome provided for the radar apparatus, a front wiper, a wiper operation detector detecting an operation of the front wiper, a temperature detector detecting temperature outside of the vehicle, and a processing unit. The processing unit estimates whether sensitivity degradation of the radar apparatus is caused, based on the detecting result of the wiper operation detector and the detecting result of the temperature detector.
Here, the radar system mounted on a vehicle may further include an output unit. At this time, the processing unit notifies that the sensitivity degradation of the radar apparatus is caused, to, a driver via the output unit based on the estimating result.
Also, the radar system mounted on a vehicle may further include a radome heater provided for the radome, and a radome heater control circuit controlling the radome heater to be turned on in response to a heater control signal. At this time, the processing unit outputs the heater control signal to the radome heater control circuit when it is estimated that the sensitivity degradation of the radar apparatus is caused.
Also, the radar system mounted on a vehicle may further include a radome wiper provided for the radome, and a radome wiper control circuit controlling the radome wiper to be turned on in response to a wiper control signal. At this time, the processing unit outputs the wiper control signal to the radome wiper control circuit when it is estimated that the sensitivity degradation of the radar apparatus is caused.
Also, the processing unit may include a first counter, a first estimating section, a second estimating section. The first estimating section estimates whether snow falls, based on the detecting result of the wiper operation detector and the detecting result of the temperature detector, and increments the first counter when it is estimated that the snow falls. The second estimating section estimates whether the sensitivity degradation of the radar apparatus is caused, based on a value of the first counter. In this case, the processing unit further include a second counter. At this time, the first estimating section estimates whether sleet falls, based on the detecting result of the wiper operation detector and the detecting result of the temperature detector, and increments the second counter when it is estimated that the sleet falls. The second estimating section estimates whether the sensitivity degradation of the radar apparatus is caused, based on the first counter value and a value of the second counter. Also, in this case, the first estimating section estimates whether rain falls, based on the detecting result of the wiper operation detector and the detecting result of the temperature detector. Also, the first estimating section decrements the first and second counters by first and second values, respectively, and also increments the second counter by a third value, when it is estimated that the rain falls. The second estimating section estimates whether the sensitivity degradation of the radar apparatus is caused, based on the first counter value and a value of the second counter.
In order to achieve another aspect of the present invention, a radar system mounted on a vehicle includes a radar apparatus, a radome provided for the radar apparatus, a speed detector detecting a running speed of the vehicle, a front wiper, a wiper operation detector detecting an operation of the front wiper, an temperature detector detecting temperature outside of the vehicle, and a processing unit. The processing unit estimates whether sensitivity degradation of the radar apparatus is caused, based on the detecting result of the wiper operation detector, the detecting result of the temperature detector, and the detecting result of the speed detector.
Here, the radar system mounted on a vehicle may further include an output unit. At this time, the processing unit notifies that the sensitivity degradation of the radar apparatus is caused, a driver via the output unit based on the estimating result.
Also, the radar system mounted on a vehicle may further include a radome heater provided for the radome, and a radome heater control circuit controlling the radome heater to be turned on in response to a heater control signal. At this time, the processing unit outputs the heater control signal to the radome heater control circuit when it is estimated that the sensitivity degradation of the radar apparatus is caused.
Also, the radar system mounted on a vehicle may further include a radome wiper provided for the radome, and a radome wiper control circuit controlling the radome wiper to be turned on in response to a wiper control signal. At this time, the processing unit outputs the wiper control signal to the radome wiper control circuit when it is estimated that the sensitivity degradation of the radar apparatus is caused.
Also, the processing unit includes a first counter, a first estimating section and a second estimating section. The first estimating section determines whether the vehicle runs faster than a predetermined speed, and estimates whether snow falls, based on the detecting result of the wiper operation detector and the detecting result of the temperature detector. Also, the first estimating section increments the first counter when it is determined that the vehicle runs faster and when it is estimated that the snow falls, and decrements the first counter when it is determined that the vehicle does not run faster. The second estimating section estimates whether the sensitivity degradation of the radar apparatus is caused, based on a value of the first counter. In this case, the processing unit may further include a second counter. At this time, the first estimating section estimates whether sleet falls, based on the detecting result of the wiper operation detector and the detecting result of the temperature detector. Also, the first estimating section increments the second counter when it is estimated that the sleet falls. Moreover, the first estimating section decrements the first and second counters and increments the second counter by a quantity corresponding to the decrement of the first counter, when it is determined that the vehicle does not run faster. The second estimating section estimates whether the sensitivity degradation of the radar apparatus is caused, based on the first counter value and a value of the second counter. Further, the first estimating section estimates whether rain falls, based on the detecting result of the wiper operation detector and the detecting result of the temperature detector. Also, the first estimating section decrements the first and second counters by first and second values, respectively, and also increments the second counter by a third value, when it is estimated that the rain falls or when it is determined that the vehicle does not run faster. The second estimating section estimates whether the sensitivity degradation of the radar apparatus is caused, based on the first counter value and a value of the second counter.
In order to still another aspect of the present invention, a method of keeping a sensitivity of a radar apparatus mounted on a vehicle, is attained by incrementing or decrementing first and second counters based on weather and running speed of the vehicle, the first counter indicating a snow accretion on a radome for the radar apparatus and the second counter indicating an ice on the radome, by comparing a value of each of the first and second counters with at least one threshold value, and by removing snow or ice from radome based on the comparing result.
Here, the method may further include a step of notifying to a driver that the sensitivity degradation of the radar apparatus is caused, based on the comparing result.
Also, the removing step may be attained by heating a radome heater provided for the radome. Instead, the removing step may be attained by driving a radome wiper provided for the radome.
Also, each of the first and second counters may be provided a plurality of threshold values. At this time, the removing step may be attained by activating at least one of a radome heater and a radome wiper which are both provided for the radome, based on the first and second counter values and the plurality of threshold values.
Also, the incrementing or decrementing step may be attained by detecting temperature outside of the vehicle, by estimating whether or not snow falls, whether or not sleet falls, whether or not rain falls to detect a falling state of snow, sleet or rain, by detecting the running speed of the vehicle, and by incrementing or decrementing the first and second counters based on the running speed of the vehicle, the temperature and the falling state. In this case, the estimating step may be attained by detecting an operation of a front wiper, and by detecting the falling state based on the detected operation of the front wiper and the temperature.
Here, the incrementing or decrementing step may be attained by decrementing the first and second counter by first and second values, respectively, when the vehicle does not run faster than a predetermined speed, and by incrementing the second counter by a third value, when the vehicle does not run faster than the predetermined speed.
Also, the incrementing or decrementing step may be attained by decrementing the first and second counter by first and second values, respectively, when the temperature is higher faster than a predetermined temperature, and by incrementing the second counter by a third value, when the temperature is higher faster than the predetermined temperature.
Also, the incrementing or decrementing may be attained by incrementing the first counter when the vehicle runs faster than the predetermined speed and when snow falls.
Also, the incrementing or decrementing step may be attained by incrementing the second counter when the vehicle runs faster than the predetermined speed and when sleet falls.
Also, the incrementing or decrementing step may be attained by decrementing the first and second counter by first and second values, respectively, when the vehicle runs faster than a predetermined speed and when rain falls, and by incrementing the second counter by a third value, when the vehicle runs faster than the predetermined speed and when rain falls.